Bring 2 quarts of water to boil on the stove. Once boiling, add your pasta and cook according to package instructions. Reserve 1 cup pasta water before draining.

Remove the sausage from its casing. Heat the oil in a large skillet over medium heat and add the sausage.

Cook the sausage until cooked through. Break up the sausage with a wooden spoon or meat chopper so you have bite-sized pieces once cooked through, about 5 minutes. Transfer the sausage to a plate.

Return the pan to the stove and add the onion, garlic and cherry tomatoes. Cook until the onions have softened, about 3 minutes.

Add the sausage back into the pan, along with the pasta and spinach. Add about 1/4 cup of pasta water and cook together until the spinach has wilted. Remove from the heat and add the parmesan and additional pasta water if needed (you're looking for a kind of saucy/creamy texture). Season with salt and pepper to taste and serve immediately.